The areas of investigation are 1) cytogenetic studies of human neoplastic hematological and congenital diseases, and in members of high risk cancer families; 2) the observation of chromosome aberrations and teratogenic effects of drugs such as maytansine, azaribine and Phase I drugs using in vitro and in vivo techniques; 3) the relationship of stem cells, T cells, B cells and null cells in their growth patterns and differentiation; 4) the determination of the existence of stem cells in the peripheral blood of patients with pancytopenia; 5) the detection of chromatid exchanges in patients with xeroderma pigmentosa and in cancer families by use of BrdU and Hoechst stain #33258.